In many cases x-ray detection devices are used when registering x-ray images within the context of medical navigation. Such devices enable the determination of when (and therefore the relative position of the patient) the image was produced so as to allow the image to be correctly assigned within the context of navigation. It is of course in principle also possible to transmit the detection signal to a receiver via cable, e.g., to a further processing unit, such as a navigation system. Such cables, however, typically are laid or otherwise provided separate in the x-ray device or registration device and, therefore, necessitate additional interfaces on the signal receiving components, which increases overall system complexity.
Another conventional approach for applications with analog x-ray image generating systems is to update the image information and to re-register when there are changes in the image contents. Such a system is known, for example, from EP 1 260 179 B1; however, many older or specific operating x-ray apparatus are still in use whose signal-to-noise ratio makes such a procedure difficult to implement or does not permit such a procedure. In cases in which the image is directly manipulated on the x-ray apparatus (e.g., scaled, rotated, flipped or contrast-enhanced), this could also lead to a “new” image being detected even though this is not the case. As a result, navigation problems may arise.